Fin pitch scaling for high voltage devices and low voltage devices on the same wafer

ABSTRACT

A semiconductor device is provided that includes a first plurality of fin structures having a first width in a first region of a substrate, and a second plurality of fin structures having a second width in a second region of the substrate, the second width being less than the first width. A first gate structure is formed on the first plurality of fin structures including a first high-k gate dielectric that is in direct contact with a channel region of the first plurality of fin structures and a first gate conductor. A second gate structure is formed on the second plurality of fin structures including a high voltage gate dielectric that is in direct contact with a channel region of the second plurality of fin structures, a second high-k gate dielectric and a second gate conductor.

BACKGROUND Technical Field

The present disclosure relates to semiconductor devices, such assemiconductor devices including fin structures. The present disclosurefurther relates to processing of fin including structures for use indevices having different applied voltages.

Description of the Related Art

The dimensions of semiconductor field effect transistors (FETs) havebeen steadily shrinking over the last thirty years or so, as scaling tosmaller dimensions leads to continuing device performance improvements.Planar FET devices typically have a conducting gate electrode positionedabove a semiconducting channel, and electrically isolated from thechannel by a thin layer of gate oxide. Current through the channel iscontrolled by applying voltage to the conducting gate. With conventionalplanar FET scaling reaching fundamental limits, the semiconductorindustry is looking at more unconventional geometries that willfacilitate continued device performance improvements. One such class ofdevice is a fin field effect transistor (finFET).

SUMMARY

In one aspect, a method of forming a semiconductor device is providedthat includes fin structures having different pitches for devices havingdifferent applied voltages on a same semiconductor substrate, i.e.,wafer. In some embodiments, the method of forming a semiconductor devicemay begin with forming a plurality of spacers having a first width usingspacer image transfer, wherein the plurality of spacers are forpatterning a plurality of fin structures from a semiconductor containingsubstrate. A block mask is formed over a first grouping of spacers in afirst region of the semiconductor containing substrate. An isotropicetch is applied to a second grouping of spacers not covered by the blockmask, wherein the isotropic etch reduces a width of at least one spacerin the second group of spacers to a second width that is less than thefirst width. The block mask is removed, and said plurality of finstructures are etched from the semiconductor containing substrate usingthe first grouping of spacers having the first width and the secondgrouping of spacers having the second width. A first plurality of finstructure having said first width etched using the first grouping ofspacers provides first fin structure for semiconductor devices having afirst applied voltage. A second plurality of fin structures having saidsecond width etched using the second grouping of spacers provides secondfin structures for semiconductor devices having a second applied voltagethat is greater than the first applied voltage.

In another embodiment, a method of forming a semiconductor device isprovided that includes fin structures having different pitches fordevices having different applied voltages on a same semiconductorsubstrate, i.e., wafer. In some embodiments, the method of forming asemiconductor device may begin with forming a plurality of finstructures each having a first width using spacer image transfer. Ablock mask is formed over a first grouping of fin structures in a firstregion of the semiconductor substrate. An isotropic etch is applied to asecond grouping of fin structures not covered by the block mask, whereinthe isotropic etch reduces a width of at least one fin structure in thesecond group of fin structures to a second width that is less than thefirst width. The block mask is removed. The first grouping of finstructures is processed to provide first semiconductor devices having afirst applied voltage. The second grouping of fin structures isprocessed to provide second semiconductor devices having a secondapplied voltage that is greater than the first applied voltage.

In another aspect of the present disclosure, a semiconductor device isprovided that includes a first plurality of fin structures having afirst width in a first region of a substrate, and a second plurality offin structures having a second width in a second region of thesubstrate, the second width being less than the first width, wherein thefirst plurality of fin structures and the second plurality of finstructures have substantially a same pitch. A first gate structure isformed on the first plurality of fin structures including a first high-kgate dielectric that is in direct contact with a channel region of thefirst plurality of fin structures and a first gate conductor. A secondgate structure is formed on the second plurality of fin structuresincluding an oxide gate dielectric that is in direct contact with achannel region of the second plurality of fin structures, a secondhigh-k gate dielectric and a second gate conductor.

BRIEF DESCRIPTION OF DRAWINGS

The following detailed description, given by way of example and notintended to limit the disclosure solely thereto, will best beappreciated in conjunction with the accompanying drawings, wherein likereference numerals denote like elements and parts, in which:

FIG. 1 is a side cross-sectional view depicting a plurality of spacerspresent over a semiconductor structure formed using spacer imagetransfer (SIT), in accordance with one embodiment of the presentdisclosure.

FIG. 2 is a side cross-sectional view depicting forming a block maskover a first grouping of spacers in a first region of the semiconductorcontaining substrate, in accordance with one embodiment of the presentdisclosure.

FIG. 3 is a side cross-sectional view depicting one embodiment of anisotropic etch applied to the second grouping of spacers not covered bythe block mask, wherein the isotropic etch reduces a width of at leastone spacer in the second group of spacers to a second width that is lessthan the first width, in accordance with the present disclosure.

FIG. 4 is a side cross-sectional view depicting removing the block mask,and etching a plurality of fin structures from the semiconductorcontaining substrate using the first grouping of spacers having thefirst width and the second grouping of spacers having the second width,in accordance with one embodiment of the present disclosure.

FIG. 5 is a side cross-sectional view depicting forming an oxide layerfor a gate dielectric of a high voltage semiconductor device on both ofthe first and second plurality of fin structures, in accordance with oneembodiment of the present disclosure.

FIG. 6 is a side cross-sectional view depicting forming a first gatestructure on the first plurality of fin structures having the firstwidth including a first high-k gate dielectric that is in direct contactwith a channel region of the first plurality of fin structures and afirst gate conductor; and forming a second gate structure on the secondplurality of fin structures including an oxide gate dielectric that isin direct contact with a channel region of the second plurality of finstructures, a second high-k gate dielectric and a second gate conductor,in accordance with one embodiment of the present disclosure.

FIG. 7 is a side cross-sectional view of forming a plurality of spacersusing spacer image transfer over a semiconductor containing substratefor being patterned into fin structures, in accordance with anotherembodiment of the present disclosure.

FIG. 8 is a side cross-sectional view of etching a plurality of finstructures into the semiconductor containing substrate using theplurality of spacers as an etch mask, wherein each of the fin structureshave a first width, in accordance with another embodiment of the presentdisclosure.

FIG. 9 is a side cross-sectional view depicting forming a block maskover a first grouping of fin structures in a first region of thesemiconductor substrate, in accordance with one embodiment of thepresent disclosure.

FIG. 10 is a side cross-sectional view depicting one embodiment of anisotropic etch being applied to a second grouping of fin structures notcovered by the block mask, wherein the isotropic etch reduces a width ofat least one fin structure in the second group of fin structures to asecond width that is less than the first width, in accordance withpresent disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments is intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “positioned on”means that a first element, such as a first structure, is present on asecond element, such as a second structure, wherein interveningelements, such as an interface structure, e.g. interface layer, may bepresent between the first element and the second element. The term“direct contact” means that a first element, such as a first structure,and a second element, such as a second structure, are connected withoutany intermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

In some embodiments, the methods and structures disclosed herein formFinFET semiconductor devices in the width of the fin structures havebeen processed according to whether the FinFET is used in a high voltageapplication or a low voltage application. A field effect transistor(FET) is a semiconductor device in which output current, i.e.,source-drain current, is controlled by the voltage applied to a gatestructure to the semiconductor device. A field effect transistor hasthree terminals, i.e., gate structure, source region and drain region.As used herein, a “fin structure” refers to a semiconductor material,which is employed as the body of a semiconductor device, in which thegate structure is positioned around the fin structure such that chargeflows down the channel on the two sidewalls of the fin structure andoptionally along the top surface of the fin structure. A finFET is asemiconductor device that positions the channel region of thesemiconductor device in a fin structure. The source and drain regions ofthe fin structure are the portions of the fin structure that are onopposing sides of the channel region of the fin structure.

It has been determined, that the integration flow for forming oxidedielectrics for gate structures used in high voltage applications ofFinFET structures can result in different FIN widths (Dfin) for thefinal device structure when compared to the fin width of the FinFETstructures used in lower voltage applications. This can be due to thedownstream process used in forming the FinFETs, e.g., thermal processfor forming the oxide layer of the gate structure in the high voltagedevices, and the oxidation stripping process for removing the oxidelayer in the low voltage devices. This can result in a smaller width forthe fin structure for the low voltage devices and a larger fin width forthe high voltage semiconductor devices. The presence of oxide gatedielectric layer on the fin structures of the high voltage semiconductordevices further reduces the space for work function metal (WFM) fill.

It has been determined that the above conditions can require a biggerfin pitch for the high voltages devices in comparison to the pitchseparating adjacent fin structures for low voltage devices in order toavoid work function metal (WFM) pinchoff between the fin structures forthe high voltage devices. As used herein, the “pitch” is the center tocenter distance separating adjacent fin structures having a parrallellength. As fin scaling increases, integration of different pitches forfin structures for low voltage and high voltage devices on the samesemiconductor substrate, e.g., system on chip (SOC), will result inextremely increased integration complexity and variation, e.g., lithoRET optimization and worse pitch walking etc. Resolution enhancementtechnologies (RET) are methods used to modify photomasks for integratedcircuits (ICs) to compensate for limitations in the lithographicprocesses used to manufacture the chips.

In some embodiments, the methods and structures provided in the presentdisclosure provide for one black mask and etch process being added to afin structure forming sequence to trim the fin width (Dfin) of the finstructures being used for high voltage applications prior to forming thegate oxide layer deposition. This provides that the fin width (Dfin) forthe fin structures for the high voltage (EG) devices is less than thefin width (Dfin) of the fin structures for the low voltage (SG) devices.With downstream processing, there may be Dfin loss, i.e., a reduction infin width, for low voltage devices, but not in the high voltage (EG)devices. In some embodiments, in the methods and structures of thepresent disclosure, following formation of the final gate structure,i.e., post replacement metal gate (RMG) processing, structurally thewidth of the fin structures (Dfin) for the high voltage (EG)semiconductor devices will be equal or less than the width of the finstructure (Dfin) for the low voltage (SG) semiconductor devices. Thiswill enable further high voltage (EG) fin pitch scaling than that byconventional integration flow. The methods and structures of the presentdisclosure are now discussed with more detail referring to FIGS. 1-10.

FIG. 1 depicts a plurality of spacers 10 a, 10 b present over asemiconductor structure, e.g., semiconductor substrate 5, formed usingspacer image transfer (SIT). In some embodiments, a hardmask layer 6 maybe present between the semiconductor substrate 5 and the plurality ofspacers 10 a, 10 b. In some embodiments, a first plurality of spacers 10a is present in a first region 15 of the semiconductor substrate 5 thatis later processed to provide low voltage (SD) semiconductor devices;and a second plurality of spacers 10 b is present in a second region 20of the semiconductor substrate 5 that is later processed to provide highvoltage (EG) semiconductor devices.

The semiconductor substrate 5 may be a bulk semiconductor substrate. Insome embodiments, the semiconductor substrate 5 may be composed of atype IV semiconductor material or a compound semiconductor material. By“type IV semiconductor” it is meant that the semiconductor materialincludes at least one element from Group IVA (i.e., Group 14) of thePeriodic Table of Elements. Examples of type IV semiconductor materialsthat are suitable for the fin structure include silicon (Si), germanium(Ge), silicon germanium (SiGe), silicon doped with carbon (Si:C),silicon germanium doped with carbon (SiGe:C) and a combination thereof.Typically, the semiconductor substrate 5 is composed of silicon (Si),e.g., single crystal silicon. One example of a compound semiconductormaterial suitable for the semiconductor substrate is a III-Vsemiconductor material. The term “III-V compound semiconductor” denotesa semiconductor material that includes at least one element from GroupIII of the Periodic Table of Elements and at least one element fromGroup V of the Periodic Table of Elements. Typically, the III-V compoundsemiconductors are binary, ternary or quaternary alloys including III/Velements. Examples of III-V compound semiconductors that can be used inthe present invention include, but are not limited to alloys of galliumarsenic (GaAs), aluminum arsenic (AlAs), indium gallium arsenic(InGaAs), indium aluminum arsenic (InAlAs), indium aluminum arsenicantimony (InAlAsSb), indium aluminum arsenic phosphorus (InAlAsP),indium gallium arsenic phosphorus (InGaAsP) and combinations thereof.

In some embodiments, the semiconductor substrate may be a bulksubstrate, as depicted in FIG. 1, or the semiconductor substrate may bea semiconductor on insulator (SOI) substrate. In an SOI substrate, asemiconductor on insulator (SOI) layer, such as a silicon layer, ispresent atop a buried dielectric layer, such as a silicon oxide layer,wherein the buried dielectric layer is present atop a base semiconductorlayer. Any of the aforementioned semiconductor materials used for thesemiconductor substrate may provide the composition of the SOI layer orthe base semiconductor layer.

The hardmask dielectric layer 6 may be composed of any dielectricmaterial, such as an oxide, nitride or oxynitride material. For example,when the hardmask dielectric layer 6 is an oxide, the hardmaskdielectric layer 6 may be silicon oxide. In another example, when thehardmask dielectric layer 6 is a nitride, the hardmask dielectric layer6 may be composed of silicon nitride. It is noted that the abovecompositions for the hard mask dielectric layer are provided forillustrative purposes only, as other dielectric materials typically usedin semiconductor devices are equally applicable, such as aluminum oxide,silicon carbon boron nitride (SiCBN), hafnium oxide, etc. The hardmaskdielectric layer 6 may have a thickness of 1 nm to 10 nm, and may bedeposited using a chemical vapor deposition (CVD) process, such asplasma enhanced chemical vapor deposition (PECVD) or metal organicchemical vapor deposition (MOCVD). In some embodiments, the hardmaskdielectric layer 6 may be omitted.

Still referring to FIG. 1, the spacers 10 a, 10 b may be formed atop thesubstrate 10 using a spacer image transfer process. The SIT process caninclude forming a mandrel material layer (not shown) on the materiallayer that provides the fin structures, such as the SOI layer of an SOIsubstrate, or the bulk semiconductor substrate 5 upper surface. Themandrel material layer can include any material (semiconductor,dielectric or conductive) that can be selectively removed from thestructure during a subsequently performed etching process. In oneembodiment, the mandrel material layer may be composed of amorphoussilicon or polysilicon. In another embodiment, the mandrel materiallayer may be composed of a metal, such as, e.g., aluminum (Al), tungsten(W), or copper (Cu). The mandrel material layer can be formed by adeposition method, such as chemical vapor deposition or plasma enhancedchemical vapor deposition. In one embodiment, the thickness of themandrel material layer can be from 50 nm to 300 nm. Following depositionof the mandrel material layer, the mandrel material layer can bepatterned by lithography and etching to form a plurality of mandrelstructures over the topmost surface of the semiconductor containingmaterial, e.g., overlying the semiconductor substrate 1, that providesthe fin structures.

The SIT process may continue by forming a dielectric spacer 10 a, 10 bon each sidewall of each mandrel structure. The dielectric spacer 10 a,10 b can be formed by deposition of a dielectric spacer material, andthen etching the deposited dielectric spacer material. The dielectricspacer material may comprise any dielectric spacer material such as, forexample, silicon dioxide, silicon nitride or a dielectric metal oxide.Examples of deposition processes that can be used in providing thedielectric spacer material include, but are not limited to, chemicalvapor deposition (CVD), plasma enhanced chemical vapor deposition(PECVD), or atomic layer deposition (ALD). Examples of etching that beused in providing the dielectric spacers include any etching process,such as, e.g., reactive ion etching (RIE). Since the dielectric spacers10 a, 10 b are used in the SIT process as an etch mask, the width of theeach dielectric spacer 10 a, 10 b determines the width of each finstructure.

In some embodiments, the dielectric spacers 10 a, 10 b at this stage ofthe process flow have a width D1 of less than 20 nm, as measured at thebase of the dielectric spacers 10 a, 10 b. In another embodiment, thedielectric spacers 10 a, 10 b have a width D1 ranging from 5 nm to 20nm.

In some embodiments, after formation of the dielectric spacers 10 a, 10b, the SIT process continues by removing each mandrel structure. Eachmandrel structure can be removed by an etching process that is selectivefor removing the mandrel material as compared to silicon.

In some embodiments, adjacent dielectric spacers 10 a, 10 b may beseparated by a pitch P1, P2, ranging from 10 nm to 500 nm. In anotherexample, the pitch P1, P2 separating adjacent dielectric spacers 10 a,10 b may range from 20 nm to 50 nm. In this example, the pitch P1 of theadjacent dielectric spacers 10 a in the first region 15 of thesemiconductor substrate 5 is substantially the same as the pitch P2 ofthe adjacent dielectric spacers 10 b in the second region 20 of thesemiconductor substrate 5.

FIG. 2 depicts forming a block mask 25 over a first grouping ofdielectric spacers 10 a in a first region 15 of the semiconductorcontaining substrate 5. The block mask 25 does not cover the secondgrouping of dielectric spacers 10 b in the second region 20 of thesemiconductor containing substrate 5 leaving them exposed. The blockmask 25 may comprise soft and/or hardmask materials and can be formedusing deposition, photolithography and etching. In one embodiment, theblock mask 25 comprises a photoresist. A photoresist block mask can beproduced by applying a photoresist layer, exposing the photoresist layerto a pattern of radiation, and then developing the pattern into thephotoresist layer utilizing conventional resist developer. Typically,the block masks have a thickness ranging from 100 nm to 300 nm.

FIG. 3 depicts one embodiment of an isotropic etch applied to the secondgrouping of spacers 10 b not covered by the block mask 25, wherein theisotropic etch reduces a width of at least one spacer 10 b in the secondgroup of spacers to a second width D2 that is less than the first widthD1. Contrary to anisotropic etching, in which the etch rate in onedirection exceeds the remaining directions, in isotropic etching theetch rate in substantially all directions is substantially the same. Oneexample of isotropic etching processes suitable for etching the secondgroup of spacers to the second width D2 may be plasma etching.

In one embodiment, the isotropic etching of the second group of spacers10 b may laterally remove 1 nm to 4 nm from each sidewall of eachspacer, which reduces the overall width of each of the spacers in thesecond group of spacers 10 b by 2 nm to 8 nm. In another embodiment, theisotropic etching of the second group of spacers 10 b may laterallyremove 2 nm to 3 nm from each sidewall of each spacer, which reduces theoverall width of each of the spacers in the second group of spacers 10 bby 4 nm to 6 nm. In some embodiment, the second width D2 for each of thedielectric spacers 10 b at this stage of the present disclosure may beless than 15 nm, as measured at the base of the dielectric spacers 10 b.In another embodiment, the dielectric spacers 10 b have a width D2 thatis 2 nm to 5 nm less than the first width D1. Following the isotropicetching of the second group of spacers 10 b, the block mask 25 may beremoved by selective etching, chemical stripping or oxygen ashing, asdepicted in FIG. 4.

FIG. 4 depicts one embodiment of etching a plurality of fin structures30 a, 30 b from the semiconductor containing substrate 5 using the firstgrouping of spacers 10 a having the first width D1 and the secondgrouping of spacers 10 b having the second width D2 as an etch mask. Theetch process for etching the semiconductor containing substrate 5 toform the first and second group of fin structures 30 a, 30 b may be ananisotropic etch. As used herein, an “anisotropic etch process” denotesa material removal process in which the etch rate in the directionnormal to the surface to be etched is greater than in the directionparallel to the surface to be etched. The anisotropic etch may includereactive-ion etching (RIE). Reactive Ion Etching (RIE) is a form ofplasma etching in which during etching the surface to be etched isplaced on the RF powered electrode. Moreover, during RIE the surface tobe etched takes on a potential that accelerates the etching speciesextracted from plasma toward the surface, in which the chemical etchingreaction is taking place in the direction normal to the surface. Otherexamples of anisotropic etching that can be used at this point of thepresent disclosure include ion beam etching, plasma etching or laserablation. The etch process may also be timed and/or employ end pointdetection methods to determine when the etch process has recessed theexposed surfaces of the semiconductor containing substrate 5sufficiently to provide the desired height of the fin structures 30 a,30 b. The etch process is typically a selective etch. The term“selective” as used to describe a material removal process denotes thatthe rate of material removal for a first material is greater than therate of removal for at least another material of the structure to whichthe material removal process is being applied. For example, in oneembodiment, a selective etch may include an etch chemistry that removesa first material selectively to a second material by a ratio of 100:1 orgreater. In the embodiment depicted in FIG. 4, the etch process removesthe material of the semiconductor containing substrate 5, and the hardmask dielectric 6, selectively to the dielectric spacers 10 a, 10 b.

The fin structures 30 a, 30 b may have a height H1 ranging from 5 nm to200 nm. In another embodiment, the fin structures 30 a, 30 b may have aheight H1 ranging from 10 nm to 100 nm. The fin structures 30 a, 30 bhave a width D3, D4 that is dictated by the width D1, D2 of the firstand second plurality of spacers 10 a, 10 b. For example, the first widthD1 of the first plurality of spacers 10 a dictates the width D3 of thefirst plurality of fin structures 30 a, and the second width D2 of thesecond plurality of spacer 10 b dictates the width D4 of the secondplurality of fin structures 30 b. The pitch separating adjacent finstructures 30 a, 30 b is also set by the pitch P1, P2 separating theadjacent dielectric spacers 10 a, 10 b.

In some embodiments, the fin structures 30 a, 30 b may be composed of asilicon including material that provides the semiconductor substrate 1,which may include, but is not limited to silicon, single crystalsilicon, multicrystalline silicon, polycrystalline silicon, amorphoussilicon, strained silicon, silicon doped with carbon (Si:C), siliconalloys or any combination thereof. The fin structures 30 a, 30 b mayalso be composed of germanium including semiconductor materials, such assilicon germanium (SiGe) or germanium (Ge). The fin structures 30 a, 30b may also be composed of a type III-V semiconductor material, such asgallium arsenide (GaAs).

In some embodiments, the space between the adjacent fin structures 30 a,30 b is filled with a dielectric material (not shown), which may bereferred to as dielectric regions or isolation regions). The dielectricregions may be composed of a nitride, oxide, oxynitride material, and/orany other suitable dielectric layer. For example, when the dielectricregions are composed of an oxide, the dielectric regions can be siliconoxide (SiO₂). In another example, when the dielectric regions arecomposed of a nitride, the dielectric regions can be silicon nitride.The dielectric regions can be formed by a deposition process, such asCVD. Variations of CVD processes include, but not limited to,Atmospheric Pressure CVD (APCVD), Low Pressure CVD (LPCVD) and PECVD,Metal-Organic CVD (MOCVD) and combinations thereof. Alternatively, thedielectric regions 6 may be formed using a growth process, such asthermal oxidation or thermal nitridation.

The dielectric regions may be recessed using a selective etch process toprovide an exposed portion of the upper portion of the fins structures30 a, 30 b. In some embodiments, the dielectric regions are removed byan etch that is selective to the fin structures 5. The etch process forremoving the dielectric regions may be an anisotropic etch or anisotropic etch. In some examples, the etch process may be a wet chemicaletch, reactive ion etch (RIE), plasma etch, laser etch and combinationsthereof.

The dielectric spacers 10 a, 10 b, as well as the remaining portions ofthe hard mask layer 6, may be removed using a selective etch process.Planarization may also remove the dielectric spacers 10 a, 10 b.Following removal of the dielectric spacers a gate structure may beformed on the channel region of the fin structures. The gate structuremay be at least a partial replacement gate structure including at leastone sacrificial element. The term “sacrificial” as used to describe thereplacement gate conductor and replacement gate dielectric denotes thatthe structure is present during the process sequence, but is not presentin the final device structure, in which the replacement structureprovides an opening that dictates the size and geometry of a laterformed functional gate conductor and functional gate dielectric.

In the embodiment depicted in FIG. 5, an oxide layer 35 is deposited onthe first grouping of fin structures and the second grouping of finstructures. It is noted that the composition of the oxide layer and itsthickness is selected for high voltage applications. Therefore, it isnot entirely necessary that the oxide layer 35 be an oxide, and ishereafter referred to as high voltage dielectric layer 35. The highvoltage dielectric layer 35 that is present on the first group of finstructures 30 a is later removed to provide a gate structure suitablefor low voltage semiconductor devices. Therefore, the high voltagedielectric layer 35 that is present on the first group of fin structures30 a is part of the replacement gate structure in the first region 15 ofthe substrate. The high voltage dielectric layer 35 that is present onthe second group of fin structures 30 b remains in the final gatestructure that is present in the second region 20 of the semiconductorsubstrate 5, which is suitable for high voltage semiconductor devices.Therefore, the high voltage dielectric layer 35 that is present on thesecond group of fin structures 30 b is part of a functional gatestructure in the second region 25 of the substrate. The “functional gatestructure” operates to switch the semiconductor device from an “on” to“off” state, and vice versa. The functional gate structure typicallyincludes at least on gate dielectric and at least one gate conductor.

The high voltage dielectric layer 35 may be composed of any dielectricmaterial. For example, the high voltage dielectric layer 35 may becomposed of an oxide, such as silicon oxide. Silicon oxide is only oneexample of a dielectric composition that is suitable for the highvoltage dielectric layer 35. The dielectric composition of the highvoltage dielectric layer may also be composed of other oxides, such asaluminum oxide and hafnium oxide; carbon doped oxide dielectricscomprised of Si, C, O, and H (SiCOH); nitrides such as silicon nitride,boron nitride, silicon carbon boron nitride (SiCBN), and oxynitridessuch as silicon oxynitride, silicon carbon oxynitride, hafniumoxynitride; as well as combinations thereof. The high voltage dielectriclayer 35 may be deposited using chemical vapor deposition. Examples ofchemical vapor deposition that are suitable for forming the high voltagedielectric layer 35 include chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), physical vapor deposition(PVD), atomic layer deposition (ALD) and other like depositionprocesses. The high voltage dielectric layer 35 may also includematerial layers formed using a thermal growth process, such as thermaloxidation. The high voltage dielectric layer 35 may have a thicknessranging from 3 nm to 10 nm. In some embodiments, the high voltagedielectric layer 35 has a thickness that ranges from 3 nm to 5 nm.

In some embodiments, the high voltage dielectric layer 35 may be blanketdeposited on the entire substrate including the first grouping of finstructures 30 a, the second grouping of fin structures 30 b, wherein anetch process is utilized to remove the portion of the high voltagedielectric layer 35 that is present between the adjacent fin structures30 a, 30 b.

A sacrificial gate conductor may be formed on the high voltagedielectric layer 35. The sacrificial gate conductor is a component ofthe replacement gate structure for each of the first and secondplurality of fin structures 30 a, 30 b. The sacrificial material thatprovides the sacrificial gate structure may be composed of any materialthat can be etched selectively to the underlying fin structures 30 a inthe first region 15 of the semiconductor substrate 1, and the highvoltage dielectric layer 35 that is present in the second region 25 ofthe semiconductor substrate 1. In one embodiment, the sacrificialmaterial that provides the sacrificial gate conductor may be composed ofa silicon-containing material, such as polysilicon. Although, thesacrificial gate conductor is typically composed of a semiconductormaterial, the sacrificial gate conductor may also be composed of adielectric material, such as an oxide, nitride or oxynitride material,or amorphous carbon. The sacrificial material may be patterned andetched to provide the sacrificial gate conductor. Specifically, and inone example, a pattern is produced by applying a photoresist to thesurface to be etched, exposing the photoresist to a pattern ofradiation, and then developing the pattern into the photoresistutilizing a resist developer. Once the patterning of the photoresist iscompleted, the sections if the sacrificial material covered by thephotoresist are protected to provide the sacrificial gate conductor,while the exposed regions are removed using a selective etching processthat removes the unprotected regions. Following formation of sacrificialgate conductor, the photoresist may be removed. At least one dielectricgate spacer may then be formed on the sidewall of the sacrificial gatestructures. In one embodiment, the dielectric gate spacer may be formedby using a blanket layer deposition, such as CVD, and an anisotropicetchback method.

Following formation of the sacrificial gate structures, the source anddrain regions may be formed. The source and drain regions are formed onthe source and drain region portions of the fin structures. The sourceand drain region portions of the fin structures are the portions of thefin structures that are on opposing sides of the portion of the finstructure, i.e., channel portion, that the sacrificial gate structure ispresent on. As used herein, the term “drain” means a doped region insemiconductor device located at the end of the channel region, in whichcarriers are flowing out of the transistor through the drain. The term“source” is a doped region in the semiconductor device, in whichmajority carriers are flowing into the channel region. The channelregion is the region between the source and drain of a semiconductordevice that becomes conductive when the semiconductor device is turnedon. The conductivity type of the source and the drain regions typicallydictates the conductivity type of the semiconductor device. The term“conductivity type” refers to whether the device is n-type or p-type.The conductivity type of the source and drain regions typically dictatethe conductivity type of the device. For example, if the source anddrain regions are doped to an n-type conductivity, the semiconductordevice may be referred to as an n-type conductivity device, such as ann-FinFET, and if the source and drain regions are doped to a p-typeconductivity, the semiconductor device may be referred to as a p-typeconductivity device, such as a p-FinFET.

The source and drain regions may be formed by ion implanting n-type orp-type dopant into the source and drain region portions of the finstructures 30 a, 30 b. The source and drain regions may be formed byforming in-situ doped n-type or p-type conductivity epitaxialsemiconductor material on the source and drain region portions of thefin structures 30 a, 30 b. In some embodiments, a combination of ionimplantation and in-situ doped n-type or p-type conductivity epitaxialsemiconductor material may be employed to form the source and drainregions. Block masks may be utilized to isolate specific fin structures30 a, 30 b for each conductivity type doping required.

The method may continue with replacing the sacrificial gate structureswith functional gate structures 50 a, 50 b. Substituting the sacrificialgate structure with a functional gate structure may begin with formingan interlevel dielectric layer may be formed overlying the structure,and planarizing the interlevel dielectric layer to be coplanar with anupper surface of the sacrificial gate conductor of the sacrificial gatestructures. The sacrificial gate conductor may then be removed by anetch that is selective to the high voltage dielectric layer 35 that ispresent on the fins structures 35 a, 35 b. The etch may also beselective to the gate sidewall spacers. Removing the sacrificial gateconductor provides a gate structure opening to the high voltagedielectric layer on the channel region portion of the first plurality offin structures 30 a, and the second plurality of fin structures 30 b.

Referring to FIG. 6, a first functional gate structure 50 a is formed onthe first plurality of fin structures 30 a having the first width D3,and a second functional gate structure 50 b is formed on the secondplurality of fin structures 30 b having the second width D4. The firstfunctional gate structure 50 a is formed after the high voltagedielectric layer 35 is removed from the first plurality of finstructures 30 a. The first functional gate structure 50 a includes afirst high-k gate dielectric 51 that is in direct contact with a channelregion of the first plurality of fin structures 30 a, and a first gateconductor 52. The second functional gate structure 50 b that is presenton the second plurality of fin structures 30 b includes the high voltagedielectric layer 35 that is in direct contact with a channel region ofthe second plurality of fin structures 30 b, a second high-k gatedielectric 53 and a second gate conductor 54.

Forming the first and second functional gate structures 50 a, 50 b maystart with removing the high voltage dielectric layer 35 from the firstplurality of fin structures 30 a. The high voltage dielectric layer 35may be removed using an etch process that is selective to the firstplurality of fin structures 30 a. To protect the high voltage dielectriclayer 35 that is present on the second plurality of fin structures 30 bwhile the high voltage dielectric layer 35 is removed from the firstplurality of fin structures 30 a, an etch mask may be formed over thesecond region 25 of the substrate 1 covering the portion of the highvoltage dielectric layer 35 that is present therein. The etch maskleaves the first region 15 of the substrate 1, as well as the portion ofthe high voltage dielectric layer 35 exposed. The etch mask may becomposed of a photoresist material that is patterned usingphotolithography. The etch mask is similar to the block mask 25 that isdepicted in FIG. 2. Therefore, the above description of the block mask25 that is depicted in FIG. 2 is suitable for describing the etch mask.

Following the formation of the etch mask protecting the high voltagedielectric layer 35 that is present in the second region 25, a selectiveetch may remove the high voltage dielectric layer from the first region15 of the substrate 1. The etch process for removing the high-voltagedielectric layer may be an anisotropic etch or an isotropic etch that issubstantially selective to the first plurality of fin structures 30 aand the etch mask. Examples of etch processes that are suitable at thisstage of the present process include gaseous etching, plasma etching,reactive ion etching (RIE), wet etching and combinations thereof.Removing the high voltage dielectric layer 35 from the first region 15of the substrate exposes the channel region of the first plurality offin structures 30 a.

In some embodiments, the etch process for removing the high voltagedielectric layer 35 may also remove material from the first plurality offin structures 30 a. As noted above, the width D4 of each fin structurein the second plurality of fin structures 30 b is less than the width D3of the first plurality of fin structures 30 a. In some embodiments, theetch that removes some material from the first plurality of finstructures 30 a may reduce the width W3 of the fin structures in thefirst plurality of fin structures 30 a to be approximately equal to thewidth W4 of the fin structures in the second plurality of fin structures30 b. In other embodiments, the width W3 of the fin structures in thefirst plurality 30 a remains larger than the width W4 of the finstructures in the second plurality of fin structures W4.

After removing the high voltage dielectric layer 35 from the firstplurality of fin structures 30 b, the etch mask may be removed. The etchmask may be removed using selective etching, chemical stripping oroxygen ashing.

Following removal of the high voltage dielectric layer 35 from the firstplurality of fin structures 30 b, a high-k gate dielectric layer 51, 52may be formed over the channel region of the first and second pluralityof fin structures 30 a, 30 b. The high-k gate dielectric layer 51 thatis formed on the first plurality of fin structures 30 a may be formed indirect contact with the channel region of the first plurality of finstructures 30 a. The high-k gate dielectric layer 52 that is formed onthe second plurality of fin structures 30 b may be formed directly onthe high voltage dielectric layer 35 that is in direct contact with thechannel region of the second plurality of fin structures 30 b. In someembodiments, the term “high-k” denotes a dielectric material having adielectric constant greater than silicon oxide (SiO₂) at roomtemperature (20° C. to 25° C.) and atmospheric pressure (1 atm). Forexample, a high-k dielectric material may have a dielectric constantgreater than 4.0. In another example, the high-k gate dielectricmaterial has a dielectric constant greater than 7.0. In one embodiment,the high-k dielectric layer 51, 52 that is formed on the first andsecond plurality of fin structures 30 a, 30 b is composed of a high-koxide, such as, for example, HfO₂, ZrO₂, Al₂O₃, TiO₂, La₂O₃, SrTiO₃,LaAlO₃, Y₂O₃ and mixtures thereof. Other examples of high-k dielectricmaterials for the high-k dielectric layers 51, 52 that are formed on thefirst and second plurality of fin structures 30 a, 30 b include hafniumsilicate, hafnium silicon oxynitride or combinations thereof. In oneembodiment, the high-k dielectric layer 51, 52 that are formed on thefirst and second plurality of fin structures 30 a, 30 b may be depositedby chemical vapor deposition (CVD). Variations of CVD processes suitablefor depositing the high-k dielectric layer 51, 52 on the first andsecond plurality of fin structures 30 a, 30 b include, but are notlimited to, APCVD, LPCVD, PECVD, MOCVD, ALD, and combinations thereof.In one embodiment, the thickness of the high-k dielectric layers 51, 52is greater than 0.8 nm. More typically, the high-k dielectric layers 51,52 have a thickness ranging from about 1.0 nm to about 60 nm.

Still referring to FIG. 6, the method may continue with forming thefunctional gate structure 53, 54 for the first and second plurality offin structures 30 a, 30 b. The conductive material of the gate conductormay comprise polysilicon, SiGe, a silicide, a metal or ametal-silicon-nitride such as Ta—Si—N. Examples of metals that can beused as the gate conductor include, but are not limited to, Al, W, Cu,and Ti or other like conductive metals. The layer of conductive materialfor the gate conductor may be doped or undoped. If doped, an in-situdoping deposition process may be employed. Alternatively, a dopedconductive material can be formed by deposition, ion implantation andannealing. The at least one gate conductor may be formed using adeposition process. For example, when the at least one gate conductor iscomposed of a semiconductor material, the at least one gate conductormay be formed using may be formed using a deposition process, such aschemical vapor deposition (CVD). In another embodiment, when the atleast one gate conductor is composed of a metal, the at least one gateconductor is formed using a physical vapor deposition (PVD) process,such as sputtering. Examples of sputtering apparatus that may besuitable for depositing the at least one gate conductor include DC diodetype systems, radio frequency (RF) sputtering, magnetron sputtering, andionized metal plasma (IMP) sputtering.

In some embodiments, because the width D4 of the second plurality of finstructures 30 b has been reduced prior to forming the high voltagedielectric layer 35, the functional gate structure including the highvoltage dielectric layer 35, the high-k gate dielectric layer 52 and thegate conductor 52 is resistant to pinch off effects.

FIGS. 7-10 depict another embodiment of the present disclosure. In theembodiment that is depicted in FIGS. 7-10, the width D5 of the finstructures 30 d for the high-voltage semiconductor devices has beenreduced by isotropically etching a second plurality of fin structures 30d, while a first plurality of fin structures 30 c being used for the lowvoltage semiconductor devices is being protected by a block mask 25.

FIG. 7 depicts forming a plurality of spacers 10 c, 10 d using spacerimage transfer over a semiconductor containing substrate 1 for beingpatterned into fin structures. The plurality of spacers 10 c, 10 d, thatare depicted in FIG. 7 are similar to the plurality of spacers 10 a, 10b that are depicted in FIG. 1. Therefore, the description of theplurality of spacers 10 a, 10 b, as well as the spacer image transfer(SIT) method for forming the plurality of spacers 10 a, 10 b that aredepicted in FIG. 1, are suitable for the description of the plurality ofspacers 10 c, 10 d that are depicted in FIG. 7. For example, the widthD1 and pitch P1, P2 of the spacers 10 a, 10 b depicted in FIG. 1 issuitable for the width D1 and pitch of the spacers 10 a, 10 b that aredepicted in FIG. 7. The semiconductor substrate 1 that is depicted inFIG. 7 has also been described above with reference to FIG. 1.

FIG. 8 depicts etching a plurality of fin structures 30 c, 30 d into thesemiconductor containing substrate 1 using the plurality of spacers 10a, 10 b as an etch mask, wherein each of the fin structures 30 c, 20 dhas a first width D3. In this embodiment, the plurality of spacers 10 a,10 b are not isotropically etched before patterning the semiconductorsubstrate 1 to provide the first and second plurality of fin structures30 c, 30 d. Therefore, all of the fin structures 30 c, 30 d may have thesame width D3 at this stage of the process. The semiconductor substrate1 may be etched with an anisotropic etch, such as reactive ion etch(RIE), plasma etching, laser ablation, and combinations thereof. Thewidth D3 of the fin structures 30 c, 30 d at this stage of the processflow may range from 5 nm to 20 nm. The height of the fin structures 30c, 30 d at this stage of the process flow may range from 20 nm to 50 nm.Dielectric regions (not shown) may be formed between the adjacent finstructures providing isolation. Following fin structures 30 c, 30 d, thedielectric spacers 10 c, 10 d may be removed by selective etching,chemical stripping or oxygen ashing.

FIG. 9 depicting forming a block mask 25 over a first grouping of finstructures 30 c in a first region 15 of the semiconductor substrate 1,in which the second grouping of fin structures 30 d in the second region25 of the semiconductor substrate 1 are not covered by the block mask 25and remains exposed. The block mask 25 depicted in FIG. 9 is similar tothe block mask 25 that is depicted in FIG. 2. Therefore, the descriptionof the block mask 25 that is depicted in FIG. 2 is applicable for thedescription of the block mask 25 depicted in FIG. 9.

FIG. 10 depicts one embodiment of an isotropic etch being applied to asecond grouping of fin structures 30 d not covered by the block mask 25,wherein the isotropic etch reduces a width of at least one fin structurein the second group of fin structures 30 d to a second width D5 that isless than the first width D3. One example of isotropic etching processessuitable for etching the second group of fin structures 30 d to thesecond width D5 may be plasma etching. In one embodiment, the isotropicetching of the second group of fin structures 30 d may laterally remove1 nm to 4 nm from each sidewall of each fin structure, which reduces theoverall width of each of the fin structure in the second group of finstructures 30 d by 2 nm to 8 nm. In another embodiment, the isotropicetching of the second group of fin structures 30 d may laterally remove2 nm to 3 nm from each sidewall of each fin structure, which reduces theoverall width of each of the fin structures in the second group of finstructures 30 d by 4 nm to 6 nm. In some embodiment, the second width D5for each of the fin structures 30 d at this stage of the presentdisclosure may be less than 15 nm, as measured at the base of the finstructure 30 d. In another embodiment, the fin structures 30 d have awidth D5 that is less than the first width D3.

Following reducing the width of the second plurality of fin structures30 c, the first plurality of fin structures 30 c may be furtherprocessed to provide low voltage semiconductor devices, and the secondplurality of fin structures 30 d may be processed to provide highvoltage semiconductor devices. For example, a high voltage dielectriclayer may be formed on each of the first and second plurality of finstructures, as described above with reference to FIG. 5. Sacrificialgate structures may then be formed on each of the fin structures 30 c,30 d, as described above. Source and drain regions may then be formedfor each of the fin structures. The sacrificial gate structures may thenbe removed. Following the removal of the sacrificial gate structures,the high voltage dielectric layer may be removed from the channel regionof the first plurality of fin structures 30 c that provide the lowvoltage semiconductor device in the first region of the substrate 15.Functional gate structures are then formed for each of the first andsecond plurality of fin structures 30 c, 30 d, as described above withreference to FIG. 6.

For example, a high-k gate dielectric layer may be formed over thechannel region of the first and second plurality of fin structures 30 c,30 d. The high-k gate dielectric layer that is formed on the firstplurality of fin structures 30 c may be formed in direct contact withthe channel region of the first plurality of fin structures 30 c. Thehigh-k gate dielectric layer that is formed on the second plurality offin structures 30 d may be formed directly on the high voltagedielectric layer that is in direct contact with the channel region ofthe second plurality of fin structures 30 d. The description of thehigh-k dielectric layers identified by reference numbers 51, 52 in FIG.6 are suitable for use with the embodiments of the present disclosureusing the fin structures 30 c, 30 d described with reference to FIGS.7-10. The method may continue with forming the conductive material ofthe gate conductor for the functional gate structure for each of thefirst and second plurality of fin structures 30 c, 30 d. The gateconductors identified by reference numbers 53 and 54 in FIG. 6 aresuitable for use with the embodiments of the present disclosure usingthe fin structures 30 c, 30 d described with reference to FIGS. 7-10.

In another embodiment, the process sequence for forming the finFETstructure depicted in FIGS. 1-10 is formed using a gate first processsequence, which is not depicted in the supplied figures. The methoddepicted in FIGS. 1-10 is a gate last process that includes forming areplacement gate structure. In another embodiment, a functional gatestructure is formed instead of a replacement gate structure, and thefunctional gate structure remains throughout the formation of the finstructure. This is referred to as a gate first process sequence. Bothgate first and gate last process sequences are applicable to the presentdisclosure.

As depicted in FIGS. 1-10, a semiconductor device is provided thatincludes a first plurality of fin structures 30 a, 30 c having a firstwidth d3 in a first region 15 of a substrate 1, and a second pluralityof fin structures 30 b, 30 d having a second width d4, d5 in a secondregion 25 of the substrate 1, in which second width d4, d5 is less thanthe first width d3. In some embodiments, the first plurality of finstructures 30 a, 30 c and the second plurality of fin structures 30 b,30 d have substantially the same pitch P1, P2.

A first gate structure 50 a is formed on the first plurality of finstructures 30 a, 30 c, and a second gate structure 50 b is formed on thesecond plurality of fin structures 30 b, 30 d. Although FIG. 6 onlydepicts the gate structures 50 a, 50 b being formed on the first andsecond plurality of fin structures 30 a, 30 b that have been formed bythe process sequence depicted in FIGS. 1-6, the gate structures 50 a, 50b depicted in FIG. 6 may equally be present on the plurality of finstructures 30 c, 30 d formed using the method described with referenceto FIGS. 1-10.

The first gate structure 50 a includes a first high-k gate dielectric 51that is in direct contact with a channel region of the first pluralityof fin structures 30 a, 30 c and a first gate conductor 53. A secondgate structure 50 b is formed on the second plurality of fin structures30 including an oxide gate dielectric 35, also referred to as a highvoltage gate dielectric 35, that is in direct contact with a channelregion of the second plurality of fin structures 30 b, 30 d, a secondhigh-k gate dielectric 52 and a second gate conductor 54.

The first gate structure 50 a may provide the gate structure for a lowvoltage semiconductor device, such as a low voltage FinFET. In oneexample, the low voltage Fin Field Effect Transistors that may includethe first plurality of fin structures 30 a, 30 c and the first gatestructure 50 a have an applied voltage of less than 1.2 V. The secondgate structure 50 b may provide the gate structure for a high voltagesemiconductor device, such as a high voltage FinFET. In one example, thehigh voltage Fin Field Effect Transistors that may include the secondplurality of fin structures 30 b, 30 d and the first gate structure 50 bhave an applied voltage of more than 2.0 eV.

While the methods and structures of the present disclosure have beenparticularly shown and described with respect to preferred embodimentsthereof, it will be understood by those skilled in the art that theforegoing and other changes in forms and details may be made withoutdeparting from the spirit and scope of the present disclosure. It istherefore intended that the present disclosure not be limited to theexact forms and details described and illustrated, but fall within thescope of the appended claims.

What is claimed is:
 1. A method of forming a semiconductor devicecomprising: forming a plurality of fin structures from a semiconductorsubstrate using spacer image transfer, wherein each fin structure in theplurality of fin structures has a first width; forming a block mask overa first grouping of the plurality of fin structures; and applying anisotropic etch to a second grouping of the plurality of fin structuresnot covered by the block mask, wherein the isotropic etch reduces awidth of at least one fin structure in the second group of finstructures to a second width that is less than the first width, whereinthe first plurality of fin structures having the first width provides achannel region for semiconductor devices having a first applied voltage,and the second plurality of fin structures having said second widthprovides a channel region for semiconductor devices having a secondapplied voltage that is greater than the first applied voltage.
 2. Themethod of claim 1, wherein said forming the plurality of fin structuresfrom the semiconductor substrate using spacer image transfer comprises:forming a mandrel on the semiconductor substrate; forming dielectricspacers on sidewalls of the mandrel; and removing the mandrel; andetching the semiconductor substrate using the dielectric spacers as anetch mask.
 3. The method of claim 1 further comprising forming a highvoltage dielectric layer on said second plurality of fin structures. 4.The method of claim 3, wherein forming the high voltage dielectric layercomprises blanket depositing said high voltage dielectric layer on saidfirst plurality of fin structures and said second plurality of finstructures, and removing the high voltage dielectric layer from thefirst plurality of fin structures using a selective etch.
 5. The methodof claim 3, wherein the high voltage dielectric layer is an oxide. 6.The method of claim 5, wherein the high voltage dielectric layer has athickness ranging from 3 nm to 7 nm.
 7. The method of claim 4, furthercomprising forming a first high-k gate dielectric layer directly on thechannel region of the first plurality of fin structures, and forming asecond high-k dielectric layer directly on the high voltage dielectriclayer that is present directly on the channel region of the secondplurality of fin structures.
 8. The method of claim 7, furthercomprising forming a gate conductor on the first and second high-k gatedielectric layers.
 9. The method of claim 7, wherein the first appliedvoltage is less than 1.2 eV, and the second applied voltage is greaterthan 2.0 eV.
 10. A method of forming a semiconductor device comprising:forming a plurality of fin structures from a semiconductor substrate,wherein each fin structure in the plurality of fin structures has afirst width; forming a block mask over a first grouping of the pluralityof fin structures; and applying an isotropic etch to a second groupingof the plurality of fin structures not covered by the block mask,wherein the isotropic etch reduces a width of at least one fin structurein the second group of fin structures to a second width that is lessthan the first width, wherein the first plurality of fin structureshaving the first width provides a channel region for semiconductordevices having a first applied voltage, and the second plurality of finstructures having said second width provides a channel region forsemiconductor devices having a second applied voltage that is greaterthan the first applied voltage.
 11. The method of claim 10, furthercomprising forming a high voltage dielectric layer on said secondplurality of fin structures.
 12. The method of claim 11, wherein formingthe high voltage dielectric layer comprises blanket depositing said highvoltage dielectric layer on said first plurality of fin structures andsaid second plurality of fin structures, and removing the high voltagedielectric layer from the first plurality of fin structures using aselective etch.
 13. The method of claim 11, wherein the high voltagedielectric layer is an oxide.
 14. The method of claim 13, wherein thehigh voltage dielectric layer has a thickness ranging from 3 nm to 7 nm.15. The method of claim 12, further comprising forming a first high-kgate dielectric layer directly on the channel region of the firstplurality of fin structures, and forming a second high-k dielectriclayer directly on the high voltage dielectric layer that is presentdirectly on the channel region of the second plurality of finstructures.
 16. The method of claim 15, further comprising forming agate conductor on the first and second high-k gate dielectric layers.17. The method of claim 16, wherein the first applied voltage is lessthan 1.2 eV, and the second applied voltage is greater than 2.0 eV. 18.A method of forming a semiconductor device comprising: forming aplurality of fin structures from a semiconductor substrate using spacerimage transfer, wherein each fin structure in the plurality of finstructures has a first width; and applying an isotropic etch to a secondgrouping of the plurality of fin structures, wherein the isotropic etchreduces a width of at least one fin structure in the second group of finstructures to a second width that is less than the first width, whereinthe first plurality of fin structures having the first width provides achannel region for semiconductor devices having a first applied voltage,and the second plurality of fin structures having said second widthprovides a channel region for semiconductor devices having a secondapplied voltage that is greater than the first applied voltage.
 19. Themethod of claim 18, wherein said forming the plurality of fin structuresfrom the semiconductor substrate using spacer image transfer comprises:forming a mandrel on the semiconductor substrate; forming dielectricspacers on sidewalls of the mandrel; and removing the mandrel; andetching the semiconductor substrate using the dielectric spacers as anetch mask.
 20. The method of claim 18, further comprising forming a highvoltage dielectric layer on said second plurality of fin structures.